An improved approach for estimation of flow and hysteresis parameters applicable to WAG experiments

摘要

Water-alternating-gas (WAG) injection has demonstrated encouraging results for improving oil recovery. However, numerical simulation of three-phase flow and the associated hysteresis effects are not well-understood. Currently, modelling of hysteresis phenomena occurring in WAG cycles is based on updating two-phase relative permeabilities (krs) to account for three-phase characteristics, which is not a trivial task. In this work, a new assessment on the WAG-hysteresis model, which was originally developed for water-wet conditions, was carried out by automatic history-matching of two coreflood experiments in water-wet and mixed-wet conditions. Here in this work, it was attempted to estimate a set of more reliable two-phase krs within active saturation ranges of coreflood experiments performed under water-wet and mixed-wet conditions. Using the first cycle of the WAG experiments (first waterflood and the subsequent gas flood), the two-phase krs (oil/water and gas/oil) were estimated assuming minimal hysteresis occurs in the first cycle. For subsequent cycles, pertinent parameters of the WAG-hysteresis model are included in automatic history-matching process. The outcome of these historymatching exercises would indicate how the WAG-hysteresis model would perform under different wettability conditions using a more representative set of two-phase krs. Also, using these experiments, the ability of the WAG-hysteresis model in simulating the full cycles of WAG injections would be assessed. In other words, auto-history-matching of whole WAG coreflood experiments would enable integrated simulation of two and three-phase flow regions co-existing in cyclic WAG injection.